Generally, the common input device of a computer system includes for example a mouse, a keyboard device or a trackball. Via the keyboard device, the user may input characters and instructions into the computer system. As a consequence, most users and most manufacturers pay much attention to the development of keyboard devices.
Hereinafter, the configurations and functions of a conventional keyboard device will be illustrated with reference to FIG. 1. FIG. 1 is a schematic view illustrating the outward appearance of a conventional keyboard device. The surface of the conventional keyboard device 1 includes plural keys. These keys include ordinary keys 10, numeric keys 11 and function keys 12. When one or more keys are depressed by the user, a corresponding signal is issued to the computer, and thus the computer executes a function corresponding to the depressed key or keys. For example, when the ordinary keys 10 are depressed, corresponding English letters or symbols are inputted into the computer system. In addition, the function keys 12 (F1˜F12) can be programmed to cause corresponding application programs to provide certain functions.
With increasing development of science and technology, a tablet personal computer is introduced into the market. The tablet personal computer has a small-sized shape as a LCD screen. Generally, the display screen of the tablet personal computer is a touch screen. Via the touch screen, the user may input instruction to the tablet personal computer to control operations of the tablet personal computer. Generally, when the user wants to input a character or a symbol into the tablet personal computer, an on-screen keyboard is enabled and shown on the touch screen of the tablet personal computer. The on-screen keyboard is virtual keyboard simulating the real keyboard device. By touching an icon of the on-screen keyboard, a corresponding character or symbol is inputted into the tablet personal computer. In other words, characters or symbols may be directly inputted into the tablet personal computer without any external keyboard device.
Although the tablet personal computer is easily carried because it has a small-sized shape and no external keyboard device is needed, there are still some drawbacks. For example, the use of the touch screen to input characters or symbols becomes hindrance for most users who are familiar with the common personal computers or notebook computers. Consequently, in many circumstances, an external keyboard device that has functions and configurations similar to the keyboard device as shown in FIG. 1 is connected to the tablet personal computer. In addition, the tablet personal computer is placed and supported on a prop stand (e.g. a bookshelf). That is, the tablet personal computer is usually considered as a common display screen, and the external keyboard device is used for inputting characters or symbols. Generally, the external keyboard device is connected with the tablet personal computer via a universal serial bus (USB) connection.
Although the external keyboard device may facilitate the user to operate the tablet personal computer in the usual practice, there are still some drawbacks. For example, the external keyboard device and the tablet personal computer need to be simultaneously carried. If the external keyboard device is not simultaneously carried with the tablet personal computer, the user has no choice but to input characters or symbols through the on-touch keyboard of the touch screen. From the above discussions, if the user wants to operate the tablet personal computer in the usual practice, the external keyboard device should be additionally carried. If the user does not want to additionally carry the external keyboard device, the user needs to directly input characters or symbols through the on-touch keyboard of the touch screen The above two approaches, however, are not user-friendly.
Therefore, there is a need of providing an easily-carried and easy-to-use keyboard device for use with a tablet personal computer so as to obviate the drawbacks encountered from the prior art.